.page {
  width: 1600px;
  border: 2px solid;
  margin: auto;
}
.page p {
  text-indent: 2rem;
}
.page1 {
  background: lightblue;
}
.page2 {
  background: lightgreen;
}
.nav {
  position: fixed;
  left: 0;
  top: 50%;
  transform: translateY(-50%);
  color: #fff;
  background: #008c8c;
  padding: 20px;
}
.nav a {
  color: inherit;
  display: block;
  text-decoration: none;
  margin: 20px 0;
}
.nav a.active {
  color: yellow;
}
